Elastic Block Storage (EBS) is a high-performance, low-latency block storage service provided by Alibaba Cloud for Elastic Compute Service (ECS). EBS supports random read and write to meet the data storage requirements of your business. EBS devices can be used as physical hard disks. You can partition and format EBS devices and create file systems for them.
Alibaba Cloud provides a variety of EBS devices for ECS, such as cloud disks based on a distributed storage architecture and local disks located on the physical machines that host ECS instances.
|Cloud disk||Enhanced SSD (ESSD)||ESSDs are based on the next-generation distributed block storage architecture and
utilize the 25 Gigabit Ethernet and remote direct memory access (RDMA) technologies.
Each ESSD has low latency and can deliver up to 1,000,000 random read/write IOPS.
We recommend that you use ESSDs for scenarios such as online transactional processing (OLTP) databases, NoSQL databases, and Elasticsearch, Logstash, and Kibana (ELK) distributed logs.
|Standard SSD||Standard SSDs are high-performance disks that offer consistent high random IOPS and
high data reliability.
We recommend that you use standard SSDs for scenarios such as I/O-intensive applications, small and medium-sized relational databases, and NoSQL databases.
|Ultra disk||Ultra disks are cost-effective and offer medium random IOPS and high data reliability.
We recommend that you use ultra disks as system disks or for scenarios such as development and testing.
|Basic disk||Basic disks are the previous generation of disks and are unavailable for purchase.||None|
|Local disk||Local disks are physical disks attached to physical machines that host ECS instances.
Local disks provide local storage access capabilities for ECS instances. They are
suitable for business scenarios that require high storage I/O performance, a large
amount of storage, and high cost-effectiveness. Local disks offer low latency, high
random IOPS, high throughput, and high cost-effectiveness.
Note Local disks are physically located on a single physical machine. This increases the risks of single points of failure (SPOFs). The durability of data stored in a local disk is determined by the reliability of the associated physical machine. To ensure data availability, we recommend that you implement data redundancy at the application layer. You can use deployment sets to distribute ECS instances across multiple physical machines for high availability and disaster recovery.
- Data durability during read and write operations
Three copies of your business data are stored in the block storage cluster within the same zone to ensure 99.9999999% (nine 9's) data durability during read and write operations. For more information, see Triplicate storage.
- Proactive backup
You can create snapshots for disks on a regular basis to enhance your data security. Snapshots are a backup service provided by Alibaba Cloud. They back up the data stored on cloud disks, such as logs and customer transactions, for query purposes. For more information, see Snapshot overview.
- Data erasure mechanism
When you delete a piece of data, the data is completely erased from the distributed block storage system and can no longer be accessed by other users. The following mechanisms are used to ensure that deleted data is completely erased:
The storage system performs sequential writes to append data to existing files at the underlying layer of cloud disks. This mechanism makes full use of high-bandwidth and low-latency sequential writes to physical disks. If you delete a logical space from a cloud disk after data is appended at the underlying layer of the cloud disk, this operation is recorded as metadata. The storage system returns only zero for all requests of reading data from the logical space. Similarly, when you overwrite the data in a logical space of a cloud disk, the storage system does not immediately overwrite the data in the corresponding physical space, but modifies the mapping between the logical space and the physical space. This ensures that data that has been overwritten is no longer readable. Data fragments that result from delete or overwrite operations are forcibly and permanently deleted from the underlying physical disks.
When an EBS device (cloud disk) is released, the storage system immediately destroys the metadata of the device to ensure that the data is no longer accessible. At the same time, the physical storage space that corresponds to the disk is recycled. The physical storage space must be cleared before it is re-assigned to store data. Before data is written to a new cloud disk, the system returns only zero for all read requests.
- Data encryption
We recommend that you encrypt the storage devices that you use if your applications are data-sensitive. Cloud disks and their snapshots are encrypted by using keys based on the standard AES-256 algorithm. Data is automatically encrypted when it is transmitted from ECS instances to cloud disks and automatically decrypted when the data is read. For more information, see Encryption overview.
For information about the limits and quotas of EBS devices, see the "Elastic Block Storage (EBS) limits" in Limits.
|Creation phase||Create an empty cloud disk or a cloud disk that contains backup data for an ECS instance.||
|O&M phase||View the basic information and monitoring data of cloud disks.|
|Use the snapshot feature to back up and restore data stored in cloud disks.|
|Upgrade the specifications of cloud disks when the performance of the cloud disks cannot meet your requirements.|
|Resize cloud disks when the storage capacity of the cloud disks cannot meet your requirements.|
|Initialize cloud disks when you want to restore the cloud disks to their initial states.|
|Change the operating system of an instance by replacing the system disk when you want to use a new operating system.|
|Release phase||Release cloud disks to minimize costs when the disks are no longer needed.|